By far the most effective camera-for-when-you-don’t-want-to-carry-a-camera is a compact of some description; ideally one that’s small enough you don’t notice it, but is fast and responsive enough to react when you see something, and preferably be operable one-handed. I don’t want to feel like I’m carrying a camera. Of the dozens of these things I’ve owned, precisely none of them have fit the bill completely.